Shawn R. Kuchta, Duncan S. Parks,
David B. Wake, 2009Pronounced phylogeographic structure on a small spatial
scale:
Geomorphological evolution and lineage history in the salamander ring
species
Ensatina eschscholtzii in central coastal California

Molecular Phylogenetics and Evolution 50 (2009) 240–255

ABSTRACT
The salamander Ensatina eschscholtzii is a classic example of
a ring species, and has an intricate biogeographic history. Within a part
of the ring distribution, earlier work using allozymes disclosed high
levels of genetic structure in central coastal California, where the subspecies
oregonensis, xanthoptica, and eschscholtzi
meet. We used mitochondrial cytochrome b sequences to further examine
patterns of divergence in this area, including data from 155 localities
(309 individuals). Our focus is on the documentation of population-level
haplotype lineages. We show that oregonensis is represented by
two unrelated, phenotypically similar clades, both of which possess substantial
substructure of their own. The subspecies xanthoptica includes
two lineages that differ in phenotype, one of which has colonized the
foothills of the Sierra Nevada. The subspecies eschscholtzii
occurs mainly to the south, but some populations from a northern lineage
extend into the Monterey Bay region, where they approach xanthoptica
geographically. In sum, populations in the central coastal California
region form a distributional patchwork, including three subspecies, three
clades (which differ from the three subspecies), and ten haplotype lineages.
We conclude that such striking levels of phylogeographic structure reflect
interspersed episodes of spatial fragmentation, in part driven by the
complex geomorphological evolution of the California Coast Range system